Business and other functions are moving to a mobile paradigm. With the expanding use of portable computing devices and portable devices include laptops, cellular phones, and PDAs, among others, many typical portable display and portable projection devices are available. However, typical display technologies are cumbersome, have low quality, and have a high power consumption.
Many typical projection devices are large projection devices designed to be connected to a computer, often a desktop computer. With the proliferation of laptop computers, the market has expanded as the projection devices became more portable. Recently, vendors have developed devices that enable a PDA, such as a Palm or Pocket PC device, to be connected to a projector and drive a presentation, eliminating the need for a laptop computer. Likewise, many high-end projectors include the ability to store and display Powerpoint files without an external device. The typical user of these projectors is the corporate user for the presentation purposes, but the market is expanding to home theatre, specialty displays, and training simulation applications.
Display projection systems are typically large, heavy and power hungry devices. They require high-power and high-temperature light sources to work. This means they also require significant cooling and power supplies. Also, current devices require fairly complex optics to focus and manipulate the display for “keystone correction” and zoom, among other features. Manual correction of the display is required to accommodate environmental issues. Typical devices are shrinking through the use of smaller components, but essentially the technologies used are old. The problems of high-power, large size, durability, and usability remain. These typical display technologies include CRTs, LCDs, Plasma Displays, and Light Valve or DLP® Projectors.
Many typical portable projectors are the size of a large laptop in width and depth but often twice the height of many typical laptops. One typical unit is 1.9″ h×9″×7″ weighing 2.9 pounds. This devise is based on the TI DLP® (Digital Light Processor) technology, outputs 800 ANSI Lumens (a measure of display brightness), and supports XGA (1024×768) resolution. Many typical products range in price from $3000 to $10000 depending on features, brightness, and resolution.
Size and weight reductions are limited utilizing current technology. Fragile, power hungry, and expensive bulbs are required to be precisely assembled with precision optical components to make current devices. This keeps manufacturing costs high and margins low. The current devices are relegated to special use and only one or two per location are owned by a typical business. Although somewhat portable at 3 pounds, the current devices require bulb replacements every 200 or so hours of use at a cost of $200–$300.
Often, projector brightness is measured in ANSI Lumens. In projector specification sheets this measurement is labeled “brightness” but technically is a measure of luminant power. Lumens are a measure of the quantity of light, not illumination or brightness. To determine brightness, the number of lumens are divided by the area to get Lumens/sq.ft.
The specification for ANSI lumen measurement of projectors is independent of projected image size, and uses measurement from nine points around the screen to come up with an average value. Many typical display projectors are rated at between 800–1100 ANSI Lumens.
In contrast, a typical television picture has a brightness of about 20–30 Lumens/sq.ft. Comparison to an 800 ANSI lumen projector depends on the size of the displayed image. Remember, to get the brightness we divide the lumens rating by the display area. An 800 lumen projector is about as bright as a typical TV for a display size of 7½ feet assuming that the screen is not absorbing too much light.
The brightness of a typical 800 lumen projector on a screen to create a 7½ ft diagonal image (which covers 27 sq. ft.) is 30 lumens/sq. ft. (dividing 800 lumens by 27 sq. ft.). For a larger display, the image is less bright. For example, a 10 ft. diagonal size image (covers 48 sq. ft.), the same projector will have a brightness of 17 lumens/sq. ft. (800/48=17)
Many typical projectors are either LCD (Liquid-Crystal-Display) or DLP® (Digital Light Processor) projectors. Both type projectors use a high-intensity lamp that burns at a constant brightness. Each pixel of the LCD panels inside acts as a tiny shutter to block some of that light and vary the brightness on the screen. DLP® projectors have an array of the tiny mirrors and the light is either aimed through the lens onto the screen or aimed at a black “light sink” in the projector to absorb the unneeded light. Whether one pixel or all pixels are transmitting maximum light the bulb brightness will not vary. (Because the LCD Pixels cannot completely block the light, and DLP® projectors leak light even when the pixel's mirror is pointing toward the light sink, both types of projectors typically produce a less than perfect black.)
A 100 W light bulb puts out only 5–7 W of visible light, the rest of the energy is wasted in heat. The 100 W bulb emits the equivalent of about 800 lumens, but a projector that outputs 800 lumens typically requires a 250 W bulb. This is because the bulb outputs light in all directions. Imperfections in the reflector, leakage of light, and the light absorbed going through the LCD panel and the lenses waste about half of the luminous intensity before it leaves the projector. Also, some light is lost in dispersion as it crosses the room to the screen. Getting the light from the bulb to the screen wastes a lot of energy.
To get a very “white” color from a bulb the filament must operate at a high temperature which requires higher voltages and a much larger power supply. This also increases the power lost as heat.
The difference between many typical projectors and many typical televisions is the projection method. In a television CRT (Cathode-Ray-Tube), light is created by a focused beam of electrons hitting the phosphor on the inside of its face. The beam illuminates a very small point and moves that point rapidly across the faces from left to right, top to bottom until it covers the whole surface. This takes place rapidly so the eye doesn't notice and sees the picture as one solid image.
The electron beam intensity is varied as needed to change the brightness of the dot. The primary limitation of brightness in a CRT is its maximum beam current. The average power required to create a complete picture is much lower. If only 10% of the screen needs to be at maximum brightness, then maximum power is required for only 10% of the time. For a scanning type display two measurements are needed, average power (the equivalent to ANSI lumens) and peak power. The average power can be much lower for the same quality picture because it is rarely required that the whole screen be white.
There are CRT based projectors, which typically use 3 very bright CRTs, focused through lenses to project an image. However, they are heavy and large. CRTs are sometimes still used for rear-projection TVs. The peak to average (ANSI) lumens ratio of CRT projectors is typically five to one. For example, a 160 ANSI lumen rated CRT projector will have over 800 peak lumens. Since CRTs can completely cut off the beam current, CRTs can provide a perfect black level. A clean black is just as important to picture quality as a bright white. Because of the basic difference, a CRT projector with a typical, 160-lumen ANSI brightness and 800-plus peak brightness, will actually look brighter than an LCD projector rated at 800 lumens.
Early computer monitors (green screens) could not scan the number of lines required often enough, (at a high-enough refresh rate) so they had phosphors with more persistence. (i.e. they glowed longer after the electron beam hit them.) High persistence phosphors were required to overcome limitations of the electronics and are designed to improve display quality when the device cannot scan fast enough.
All phosphors have some persistence, which is unavoidable. Paradoxically, as display electronics got faster and could drive the beam more quickly (i.e. higher refresh rates), CRT manufacturers have had to work to minimize the persistence of the phosphors in CRTs. Computer monitors have increasingly used lower persistence phosphors at higher refresh rates so they get less image flicker and crisper images of moving pictures like video.
In addition to the display issues, connection to devices may prove problematic. Typical display devices for laptops use connections that are not available for other portable computing devices. Cross compatibility is limited and multiple display devices must be used for multiple portable devices.
These problems persist in many display arenas including heads-up displays, gauge displays, rear projection televisions, front projection televisions, computer monitors, cell phone screens, PDA screens, portable projection devices, and photocopier imaging, among others. As such, this solution may be applied to a variety of display applications.
As such, many typical display devices suffer from the display capabilities, interface formats, and portability. Further, many typical displays are bulky, heavy, expensive, high power consumers, high heat producers, mechanically complex, difficult to setup, and/or fragile, among others. Many other problems and disadvantages of the prior art will become apparent to one skilled in the art after comparing such prior art with the present invention as described herein.